JPH06253233A - Signal demodulator - Google Patents

Abstract

(57) [Summary] [Object] To provide a signal demodulating device capable of automatically adjusting a fluctuation in a signal level caused by a variation in an attenuation amount of a delay line. [Structure] An input terminal 21, and a delay line 22 for outputting a delayed signal obtained by delaying a signal input from the input terminal 21,
The delay signal output from the delay line 22 is given, amplified by an amplification factor based on the control signal, and output as an amplified signal A
The GC amplifier 24 and the amplified signal output from the AGC amplifier 24 are provided, and the amplitude of the amplified signal is detected to detect the first signal.
A peak detector 26 that outputs an amplitude detection signal of No. 1, a peak detector 27 that receives the signal input from the input terminal 21, detects the amplitude of this signal, and outputs a second amplitude detection signal, Amplifier 29 for controlling the amplification factor by outputting a control signal based on the relative potential difference between the amplitude detection signal of No. 2 and the second amplitude detection signal to the AGC amplifier 24 to output the control signal.
With.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal demodulating device.

[0002]

2. Description of the Related Art PAL (ph
An example of a signal demodulation device is shown in FIG. Variable resistor R1 at the input terminal 11,
The delay line 12 and the signal line 13 are connected in series, and the signal line 14 is connected to the input terminal 11 in parallel with the delay line 12. The signal line 13 and the signal line 14 are respectively connected to two input terminals of the demodulation circuit 15, and the output terminal of the demodulation circuit 15 is connected to the output terminal 16 of the device.

The PAL chroma signal input from the input terminal 11 passes through the variable resistor R1 and the delay line 12 and is delayed by about 63.5 (μsec) corresponding to one horizontal line. The PAL chroma signal input from the above is input to the demodulation circuit 15 as a direct signal, and the demodulated signal is output from the output terminal 16 to the outside of the device.

Here, a glass delay line or the like is used as the delay line 12, but there are variations in the attenuation amount due to manufacturing errors and the like. The variation in the attenuation amount of the delay line 12 causes a difference between the amplitude of the delayed signal transmitted through the signal line 13 and the amplitude of the direct signal transmitted through the signal line 14. Therefore, the variation of the attenuation amount of the delay line 12 is adjusted by using the variable resistor R1 so that the amplitudes of both signals are made equal to each other.

However, it is inconvenient to manually adjust each product by using the variable resistor R1 and the cost is increased.

Further, the resistance value of the delay line 12 changes with time. It was difficult to deal with such a change in the attenuation amount by the adjustment using the variable resistance value R1.

[0007]

As described above, in the conventional signal demodulation device, the variation in the attenuation amount of the delay line 12 is dealt with manually for each item, so that the cost is increased and at the same time the attenuation is performed. There is a problem that it is difficult to cope with the change in the amount with time.

The present invention has been made in view of the above circumstances, and provides a signal demodulating device capable of coping with fluctuations in the amplitude of a delay signal caused by variations in the attenuation amount of a delay line without human intervention. The purpose is to do.

[0009]

A signal demodulating device of the present invention comprises an input terminal to which a signal is inputted from the outside, and a delay means which is connected to the input terminal and outputs a delayed signal obtained by delaying the signal for a predetermined time. And the amplification signal output from the amplification means and the amplification signal output from the amplification means, the amplification signal being amplified by an amplification factor based on a control signal to be described later, and the amplification signal output from the amplification means. A first amplitude detecting means for detecting the amplitude of the amplified signal and outputting a first amplitude detection signal; and the signal input from the input terminal, and detecting the amplitude of the signal to generate a second amplitude detecting signal. First amplitude detection means for outputting an amplitude detection signal of
Generating the control signal based on a relative potential difference between the second amplitude detection signal output from the second amplitude detection means and the second amplitude detection signal output from the second amplitude detection means. Differential amplification means for controlling the amplification factor by giving it to the amplification means.

[0010]

When there is a variation in the attenuation amount of the delay means, the amplitude of the delay signal output from the delay means, and
Although the amplitude of the signal input from the input terminal does not match, by detecting the amplitudes of these two signals and applying a control signal based on the difference to the amplification means to control the amplification factor,
Can be automatically adjusted to match.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of the signal demodulating device according to the present embodiment. The delay line 22 is connected to the input terminal 21, and the non-inverting input terminal of the automatic gain control amplifier (AGC Amp) 24 is connected to the output terminal of the delay line 22 via the signal line 23. One inverting input terminal of the automatic gain control amplifier 24 is grounded. The output terminal of the automatic gain control amplifier 24 is connected to the peak detector 26 by the signal line 30.
Is connected to the input terminal of.

The input terminal 21 is connected to the input terminal of the peak detector 27 via a signal line 25. Demodulation circuit 2
A signal line 30 and a signal line 25, which are connected to the output terminal of the automatic gain control amplifier 24, are connected to the two input terminals of the signal line 8. The output terminals of the peak detectors 26 and 27 are
The differential amplifier 29 is connected to the non-inverting input terminal and the inverting input terminal, respectively. The output terminal of the differential amplifier 29 is
It is connected to the control terminal of the automatic gain control amplifier 24.
In addition, the peak detectors 26 and 27 have burst gates 3
The burst signals output from 1 are input.

The operation of this embodiment having such a configuration will be described below. The PAL chroma signal is input to the input terminal 21, passes through the delay line 22 and is delayed by one horizontal line, and then is input to the non-inverting input terminal of the automatic gain control amplifier 24 via the signal line 23 as a delay signal. . The relative potential difference of the delayed signal with respect to the ground voltage input to the inverting input terminal is amplified and input to the peak detector 26 via the signal line 30 from the output terminal. On the other hand,
The PAL chroma signal input from the input terminal 21 is input to the peak detector 27 from the signal line 25 as a direct signal.

The burst signals are input to the peak detectors 26 and 27 as described above, and the amplitudes of the delayed signal and the direct signal are detected in accordance with the timing defined by these signals. The amplitudes of the delayed signal and the direct signal detected by the peak detectors 26 and 27 are input to the non-inverting input terminal and the inverting input terminal of the differential amplifier 29, respectively. The differential amplifier 29 amplifies the relative potential difference between the amplitude of the delayed signal and the amplitude of the direct signal, and inputs the amplified potential difference to the control terminal of the automatic gain control amplifier 24. The automatic gain control amplifier 24 adjusts the amplitude of the delay signal given from the delay line 22 based on the potential difference between these two signals. As a result, the amplitude of the delay signal and the amplitude of the direct signal are automatically adjusted so that they match. In this way, the delayed signal and the direct signal having the same amplitude are input to the demodulation circuit 28, and the demodulated signal is output from the output terminal 32 to the outside.

According to this embodiment, the variable resistor required in the conventional device is unnecessary, and it is not necessary to manually adjust the amplitudes of the delay signal and the direct signal for each product, which contributes to cost reduction. can do. Further, even if the attenuation amount of the delay line 22 changes, the amplitude is automatically adjusted at any time, so that it is possible to cope with a change over time.

The above-described embodiments are merely examples and do not limit the present invention. For example, in the present embodiment, the peak detector is used as the amplitude detecting means, but this may be any one that can detect the amplitude of the input signal, and for example, a low-pass filter or the like is used to calculate the average voltage according to the amplitude. It may be detected.

[0017]

As described above, the signal demodulating device according to the present invention delays by the amplitude of the input signal and the delaying means even when the attenuation amount of the delaying means for delaying the input signal varies. The amplitude of these two signals can be automatically matched by controlling the amplification factor of the means for amplifying the delayed signal so that the amplitude of the delayed signal matches. The adjustment is unnecessary and the cost is reduced, and it is possible to cope with the change of the attenuation amount with time.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a signal demodulating device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a conventional signal demodulation device.

[Explanation of symbols]

 21 Input Terminal 22 Delay Line 23, 25, 30 Signal Line 24 Automatic Gain Control Amplifier 26, 27 Peak Detector 28 Demodulator 29 Differential Amplifier 31 Burst Gate 32 Output Terminal

Claims (1)

[Claims] 1. An input terminal for receiving a signal from the outside, a delay means connected to the input terminal for outputting a delay signal obtained by delaying the signal for a predetermined time, and the delay signal output from the delay means. Given,
Amplifying means for amplifying and outputting as an amplified signal at an amplification rate based on a control signal described later, and given the amplified signal output from the amplifying means,
First amplitude detection means for detecting the amplitude of the amplified signal and outputting a first amplitude detection signal, and the signal input from the input terminal are given, and the amplitude of this signal is detected to detect the second amplitude. Second amplitude detection means for outputting an amplitude detection signal, the first amplitude detection signal output from the first amplitude detection means, and the second amplitude output from the second amplitude detection means A signal demodulating device comprising: a differential amplifying means for controlling the amplification factor by generating the control signal based on a relative potential difference from a detection signal and giving the control signal to the amplifying means.